The ultimate objective of gene therapy is the correction of human disease precisely at the tissue sites which manifest the disorder. We are developing organ-specific gene therapies for hemophilia and other diseases using vectors based upon recombinant Adeno-Associated Virus (rAAV). We have made substantial progress during the past year. In vivo evaluation of rAAV has been difficult, because it has been impossible to prepare the recombinant virus in high titer. We developed a novel strategy that permitted us to analyze rAAV in vivo even while using these low viral dosages. Significantly, this strategy of focused vector delivery permitted gene transfer to be accomplished in mice using techniques that are directly relevant to future potential applications in human patients. We utilized a gallbladder catheter to selectively deliver a vector expressing the nuclear localized LacZ gene to one or more hepatobiliary tissue targets. We initially used recombinant adenovirus because it is easily prepared in high titer. We were able to achieve organ-selective gene transfer to hepatobiliary tissue-targets, including the liver, gallbladder, cystic duct, common bile duct, pancreas, and duodenum. We subsequently used rAAV, and achieved gene transfer to hepatocytes, hepatic cholangiocytes, and common bile duct smooth muscle cells. This unique strategy is being extended by utilizing rAAV encoding the gene for human Coagulation Factor IX.